How to edit "Posted on" text?

Hey,
So I wanted to change the “posted on…” text that shows in my posts. Well, it’s really not changing it but adding a “by Evan” text after “posted on…”
For instance, it’s currently like “Posted on 07/03/2013”. But I wanted to add “by Evan” after that.
I hope it doesn’t sound messy and that it’s doable. Also, if there are any tutorials in how to stylize the “posted on” text or how to switch the placement of date and time, I’d appreciate if you guys could post it here.
Regards,
E